Test stand for internal combustion engines



Sept. 29, 1942..

F. WENDT ETAL TEST STAND FOR INTERNAL COMBUSTION ENGINES Filed Oct. 8,1938 2 Sheets-Sheet l 1 596% in/6723073 FRlEDRICH UEHDT J'AKOB HAUG'Mun-n 23s p 1942- F. WENDT ETAL TEST STAND FOR INTERNAL COMBUSTIONENGINES Filed Oct. 8, 1938 2 Sheets-Sheet 2 .9. Fgza RRG:

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Patented Sept. 29, 1942 TEST STAND FOR INTERNAL COMBUSTION ENGINESFriedrich Wendt, Jakob Hang, Karl Kohlbecker, and Eduard .Seppeler,Berlin, Germany; vested in the Alien Property Custodian ApplicationOctober 8, 1938, Serial No. 233,964 In Germany April 19, 1937 17 Claims.

This invention relates to a test stand for in-- ternal combustionengines, especially for aeroplane engines. The object of the inventionis. to prevent mechanical vibrations or sound waves emanating from theengine on the test stand from being transmitted to the floor, roof andsurrounding walls of the test stand structure (wind tunnel) so as toprevent the sound waves radiated by the walls of the test stand fromcausing too great annoyance to the surroundings.

Several embodiments of the invention are illustrated by way of examplein the accompanying drawings, in which:

Fig. 1 shows a wind tunnel of a test stand in longitudinal section.

Fig. 2 is a top plan view of Fig. 1.

Fig. 3 is a section on line 33 of Fig. 1.

Fig. 4 is a cross section on line 4-4 of Fig. 2.

Figs. 5 and 6 show a form .of masonry with asymmetrically arrangedacoustic chambers of different cross-sectional sizes, the various layersor courses of bricks being seen from above, partly in plan view, partlyin section.

Fig. 7 is an elevation of a wall built up of four courses includingthese various masonry layers. The form of masonry appearing in Fig. 5 atthe top corresponds to the masonry layer having the reference I in Fig.7, the form appearing in Fig. 6 at the top corresponds to the masonrylayer having reference 2 of Fig. 7, the layer appearing in Fig. 5 at thebottom corresponding to the masonry layer having the reference 3 in Fig.7, and the masonry layer shown in Fig. 6 at the bottom corresponding tothe masonry layer having references 4 in said Fig. 7.

Figs. 8 and 9 illustrate two other modifications of test stand wallsfilled up only at the corners with brick-work, Fig. 8 having two coursesand Fig. 3 three courses, each view being partly in plan view, partly insection to reveal the construction.

Fig. 10 is an elevation of the structure of Fig. 8,

' and if the front brick course is removed, said Fig. 10 will serve asan elevation of the structure of Fig. 9.

Finally, Fig. 11 is an elevation of the structure of Fig. 9.

Throughout the views, the references indicate the same or like parts.

In the practice of our invention, we construct an oscillatable stand Iwhich is arranged approximately in the middle of the wind tunnel A formeasuring the performance of an engine to be tested. The engine H withpropeller I2 is freely suspended on the oscillatable plate 13 of thestand ii. The values measured on the oscillatable stand are transmittedthrough suitable conduits to the observation room B, which is connectedwith the wind tunnel by an entrance l4 and a window IS. The air forcedthrough the wind tunnel by the propeller l2 enters through the chimneyl6 into the building and is deflected by the guide plates I! in thedirection of the wind tunnel. At the opposite end of the air tunnelsimilar guide plates H are arranged which deflect upwardly the airpassing out of the wind tunnel, whereupon the air is discharged into theatmosphere through a second chimney 18. Of course instead of pressurepropellers also draught propellers may be used, the air can thereforeenter the building also in the opposite direction through the chimneyl8. In this case of course the air is discharged into the atmospherethrough the other chimney IE.

The wind tunnel A has two pairs of swinging doors 33, 34 and 35, 35capable of being swung in the direction of the arrow heads to close offthe tunnel, but when the tunnel is in use the doors are swung to thesides as shown in Fig. 1.

The oscillating stand 10 may be fixed on a foundation grid l9 made ofsection iron, this grid may be anchored in a concrete block 20. Thefoundation grid and concrete block by their combined weight produce thecounter movement for the propeller suction or pressure. Furthermore thefoundation grid imparts sufficient longitudinal stability to theconcrete block. The whole foundation of the oscillating stand may beelastically embedded in pressed. peat plates 2|. This pressed peat bed,owing to its working capacity and the great specific pressures, absorbsthe mechanical vibrations emanating from the oscillating stand, so thatthese vibrations cannot be transmitted to the other portions of thebuilding floor 22.

The sound waves, produced by the propeller when the engine is beingbraked and which are transmitted from their place of origin in alldirections through the wind tunnel, are completely damped by a specialtype of masonry of the surrounding walls of the test stand. The type ofmasonry for the individual successive layers of masonry is illustratedin top plan view and in elevation in Figs. 5, 6 and 7. The damping isattained by forming sound chambers 23 (see bottom of Fig. 5) in thesurrounding walls of the wind tunnel. This type of construction may ofcourse be used not only for the double partition wall between two teststands but also for single surrounding walls.

These sound chambers are preferably of different cross-sectional areasand according to a preferred form of embodiment distributed absolutelyunsymmetrically throughout the interior of the masonry. In other words,in said Fig. 5, for example, the acoustic chamber 23 is shown as formedby two lateral walls having the width of one brick. Within the chamberthere lie four bricks entirely free and laterally not anywhere incontact with the containing wall, as is clearly evident from the portionshown in section. In the masonry layer at the upper part of Fig. 5 themasonry is carried out without gaps at the point of saidacousticchamber, while more to the right (at the section) the beginningof an acoustic chamber is indicated. In Fig. 6 at the bottom, anacoustic chamber is shown as formed by means of longer and shorterbricks not reaching to the middle of the wall. In Fig. 6 at the top alayer without acoustic chambers is. shown. In the individual superposedlayers the upper layer is expediently made without gaps in lieu of theacoustic chamber of the lower layer and vice versa. For the masonryaccording to a further form of the invention honey-comb bricks 24 areused, that is bricks with holes, e. g. of an area of 15-20 mm. Thesehoney-comb bricks have for their object to cause by reduction ofcross-sectional area a strong throttling of the sound waves before theypass into the sound chambers, whereas in the sound chambers themselvesthere is a sudden increase of the crosssectional area with the resultthat the sound waves are destroyed in the interior of the masonry bycontinuous reflection. Thus, an excellent sound damping from thesurroundings of the test stand building is attained.

A similar sound damping efiect can also be attained by the type ofmasonry illustrated in Figs. 8 and 9. In this masonry the honey-combbricks 24 are laid in such a manner that the holes of the neighbouringbricks extend at right angles to each other, and furthermore thecrevices between the inner bricks of the wall are filled with a suitablebinding material, such as mortar, lime, preferably cement mortar only atthe corners of the bricks, so that the greater part of the crevicesbetween the inner bricks remains unfilled so as to produce for the pres-.sure fluctuations of the air a passage out of the holes in one brickinto the holes in the neighbouring bricks extending at right angles tothe holes in the first brick. Thus, the sound waves, in beingtransmitted, have to travel along an exceptionally long path, duringwhich a continual change of direction takes place, so that the sound isconsiderably damped by repeated reflection before reaching the open. Itis to be noted that in each case, whether the holes in the bricks runtransversely of the bricks or longitudinally therein, these holes extendfully through said bricks, or from a given surface through to therespectively opposite surface on the other side or end, as the case maybe.

As already mentioned, the groups of holes in adjacent bricks may runperpendicularly to each other, so that it is possible to have the groupsof holes therein running in a vertical and horizontal direction withoutleading into the sound chambers 23, but in a general sense in adirection parallel with said chamber. Such a construction isparticularly shown in, Fig. 6 at the bottom. In order to enable thesound waves to reach the chambers 23 in spite of this arrangement, careis taken for example that the groups of holes in the adjacent brickcourses are disposed in a perpendicular direction with respect to thepreceding groups of holes and lead into the sound chambers.

The sound damping towards the roof 25 of the wind tunnel is attained bya grid of lattice work arranged in the roof. The laths 26 of preferablyapproximately 50 x 40 mms. in cross section and extending transverselyto the wind tunnel, are arranged in such a manner, that, from the middleof the wind tunnel towards the inlet and outlet chimneys l6 and IS, thespacing between the individual laths gradually reduces from about 50 to10 mms. air gap. The air in the space 21 above the lath grid isrelatively very tranquil a--s compared with the air in the wind tunnelwhen the stand is in use,

which, as in the case of the sound damping by the masonry, is due to thecontinual reduction in cross sectional area of the passages and therepeated reflection of the sound waves.

In order when two test stands are arranged directly side by side, toinsulate as far as possible one test stand, from the other againsttransmission of sound waves and to prevent one stand from influencingthe other, the wall separating the two stands is subdivided into twoseparate walls 29, 30 by,an air gap 28 e. g. about 25 cms. wide and openat the top, each wall having its own sound chambers in the mannerdescribed above. Thus, the air from one wind tunnel is prevented by theporous honey-combed structure of the walls from being sucked into thewalls of the neighbouring stand and from thereby influencing themeasurements of the neighbouring stand.

Having now particularly described and ascertained the nature of our saidinvention and in what manner the same is to be performed, we declarethat what we claim is:

1. A testing stand for internal combustion engines com-prisingsurrounding walls built of honeycomb bricks having groups of holes run-'ning through the same and being disposed in multiple courses with spacesbetween mutually facing adjacent portions of the bricks with whichgroups of said holes in said bricks communicate, while said groups ofholes in turn communicate with the interior of said stand.

2. A testing stand for internal combustion engines comprisingsurrounding walls built of honeycomb bricks of different lengths havinggroups of holes running through the same and being disposed in multiplecourses with spaces between mutually facing adjacent portions of thebricks with which groups of said holes in said bricks communicate, whilesaid groups of holes in turn communicate with the interior of ningthrough the same and being disposed in multiple courses with spacesbetween mutually facing adjacent portions of the bricks with whichgroups of said holes in said bricks communicate, while said groups ofholes in turn communicate with the interior of said stand, said spacesbetween the bricks being asymmetrically distributed over the entireinterior of the wall of said stand.

4. A double testing stand for internal combustion engines including twoclosely adjacent cooperating stands separated by means of a partitionconsisting of two upright parallel brick walls spaced apart so as tohave an air gap between them, each of said cooperating stands comprisingsurrounding walls built of honeycomb bricks having groups of holesrunning through the same and being disposed in multiple courses withspaces between mutually facing adjacent portions of the bricks withwhich groups said groups of holes in turn communicate with the interiorof said stand.

5. A testing stand for internal combustion engines comprisingsurrounding walls built of honeycomb bricks having groups of holesrunning through the same and being spaced apart to form sound dampingchambers between mutually facing adjacent portions of the bricks withwhich groups of said holes in said bricks communicate, while said groupsof holes in turn communicate with the interior of said stand.

6. A testing stand for internal combustion engines comprisingsurrounding walls built of honeycomb bricks having groups of holesrunning through the same and being spaced apart to form sound dampingchambers of different cross sectional, areas between mutually facingadjacent portions of the bricks with which groups of said holes in saidbricks communicate, while said groups of holes in turn communicate withthe interior of said stand.

7. A testing stand for internal combustion engines comprisingsurrounding walls built of honeycomb bricks having groups of holesrimning through the same and being spaced apart to form sound dampingchambers of different cross sectional areas between mutually facingadjacent portions of the bricks with which groups of said holes in saidbricks communicate, while said groups of holes in turn communicate withthe interior of said stand, said sound damping chambers beingdistributed asymmetrically throughout the entire extent of saidsurrounding walls.

8. A double testing stand for internal combustion engines including twoclosely adjacent cooperating stands separated by means of a partitionconsisting of two upright parallel brick walls spaced apart so as tohave an air gap between them, each of said cooperating comprisingsurrounding walls built of honey-comb bricks having groups of holesrunning through the same and being spaced apart to form sound dampingchambers of diflerent cross sectional areas between mutually facingadjacent portions of the brick with which groups of said holes in saidbricks communicate, while said groups of holes in turn communicate withthe interior of said stand, said sound damping chambers in each standbeing distributed asymmetrically throughout the entire extent of thesurrounding walls thereof. r

9. A testing stand according to claim 1, having the holes or channels ineach brick disposed at right angles to those of the adjacent bricks,with the joints between the inner bricks of the wall filled only at thecorners thereof with ccment mortar so that the partly filled joints andthe relatively displaced holes in said bricks form tortuous passages forthe sound wam with continual change of direction for the latter from theholes of one brick into the holes of the next adjacent brick.

10. A testing stand according to claim 1, having a ceiling over ,thestand and a grid of wooden laths extending transversely to said standand disposed at a distance above said ceiling with the distance betweenthe individual laths gradually decreasing from the middle toward theends of the stand.

11. A testing stand according to claim 1, having the sound dampingchambers of different cross sectional areas, and having a ceiling overthe stand and a grid of wooden laths extending transversely to saidstand and disposed at a distance above said ceiling with the distancebetween the individual laths gradually decreasing from the middle towardthe ends of the stand.

12. A testing stand according to claim 1, having the sound dampingchambers of different cross sectional areas and distributed absolutelyasymmetrically over the surfaces of the walls, said stand also having aceiling over the stand and a grid of wooden laths extending transverselyto said stand and disposed at a distance above said ceiling with thedistance between the individual laths gradually decreasing from themiddle toward the ends of the stand. v

13. A testing stand according to claim I, having the sound dampingchambers of different cross sectional areas and distributed absolutelyasymmetrically over the surfaces of the walls, a partition wallseparating the stand from a similar adjacent stand, with the partitionwall divided into two distinct walls separated by an air gap open at thetop, said stand also having a ceiling over the stand and a grid ofwooden laths extending transversely to said stand and disposed at adistance above said ceiling with the distance between the individuallaths gradually decreasing from the middle toward the ends of the stand.

14. A testing stand according to claim 1, having the bricks laid in suchrelative positions that the holes of the mutually adjacent bricks extendat right angles to each other, with the joints between the abutting endsof the bricks at the surface of the wall filled with cement mortar.

15. A testing stand according to claim 1, having the bricks laid atright angles to each other so that the holes of the mutually adjacentbricks extend at right angles to each other, with the joints between theabutting ends of the bricks at the surface of the wall completely filledwith cement mortar and other sides of the bricks filled with cementmortar only at the corners thereof.

16. A testing stand according to claim 1, having the sound dampingchambers of different cross sectional areas produced between the bricksdistributed absolutely asymmetrically over the surfacesofthewallssaidstandalsohavinga ceiling over the stand and a grid ofwooden laths extending transversely to said stand anddisposedatadistanceabovesaidceilingwith the distance between theindividual laths gradually decreasing from the middle toward the ends ofthe stand.

l'l. Atestingstandaccordingtoclaim 1,having the holes or channels ineach brick disposed at right angles to those of the adjacent bricks,with the joints between the abutting ends of the bricks completelyfilled with cement mortar and the joints between the inner bricks of thewall filled only at the corners thereof with cement mortar, so that thepartly filled joints and the relatively displaced holes in said bricksform tortuous passages for the sound waves with continual change ofdirection for the latter from' the holes of one brick into the holes ofthe next adjacent brick.

